The present invention relates to a gas barrier film which is primarily used as a wrapping material for foods, medicinal supplies and the like, and as a packaging material or a substrate for electronic devices and the like.
Gas barrier films are used as wrapping materials for foods, medicinal supplies and the like to avoid the influence of oxygen, water vapor, and the like which are the causes of a change in the qualities of the contents primarily. These gas barrier films are also used as packaging materials or substrates for electronic devices to avoid the event that the elements formed in liquid crystal display panels and light emitting diode (LED) display panels are deteriorated in their performance when they are in contact with oxygen and water vapor. Also, in recent years, there is the case where these gas barrier films are used to impart flexibility and shock resistance to parts currently using glass or the like.
Such a gas barrier film generally has a structure in which using a plastic film as a substrate, a gas barrier layer is formed on one surface or both surfaces of the plastic film. And, the gas barrier film is formed using various methods such as a CVD deposition, PVD deposition, and sputtering deposition. Even in the case of using any method, a current gas barrier film only has an oxygen transmission rate (OTR) of the order of 2 cc/m2/day·atm and a water vapor transmission rate (WVTR) of the order of 2 g/m2/day, which are still insufficient level in the case where it is used in applications requiring higher gas barrier characteristics.
As a method of forming a film having gas barrier characteristics on a high molecular resin substrate by dry deposition, a method of forming a silicon oxide film (silica film) or an aluminum oxide film (alumina film) by using a dry deposition method such as a plasma CVD deposition is known (for example, Japanese Patent Application Laid-Open No. 8-176326, Japanese Patent Application Laid-Open No. 11-309815 and Japanese Patent Application Laid-Open No. 2000-6301). Particularly, a plasma CVD deposition has the advantage that a silicon oxide film or an aluminum oxide film having excellent gas barrier characteristics and bending characteristics can be formed without giving thermal damages to a high molecular resin substrate.
However, because the surfaces of such a silicon oxide film or aluminum oxide film are hydrophilic, there is the problem that it is difficult to more improve oxygen transmission rate (OTR) and water vapor transmission rate (WVTR). Namely, the aforementioned oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) are said to be determined by the adsorbent of the surface of a gas barrier layer to water and the diffusion coefficient of the gas barrier layer to itself. Here, the aforementioned silicon oxide film and aluminum oxide film greatly contributes to gas barrier characteristics from the viewpoint of diffusion coefficient. However, a vacuum deposition film of an inorganic oxide such as a silicon oxide film is hydrophilic in general so that water tends to adhere to the surface and there is therefore a problem that this adversely affects the gas barrier characteristics.